Merge pull request #1628 from michaeljbishop/pread-fix2

Fixes in pread()

4 files changed, 16 insertions, 0 deletions

diff --git a/src/library_fs.js b/src/library_fs.js
index 8bf0a83a..84a5245b 100644
--- a/src/library_fs.js
+++ b/src/library_fs.js
@@ -1367,7 +1367,10 @@ mergeInto(LibraryManager.library, {
           throw new FS.ErrnoError(ERRNO_CODES.EIO);
         }
         var contents = stream.node.contents;
+        if (position >= contents.length)
+          return 0;
         var size = Math.min(contents.length - position, length);
+        assert(size >= 0);
         if (contents.slice) { // normal array
           for (var i = 0; i < size; i++) {
             buffer[offset + i] = contents[position + i];
diff --git a/src/library_memfs.js b/src/library_memfs.js
index 354f5e95..28178d9f 100644
--- a/src/library_memfs.js
+++ b/src/library_memfs.js
@@ -177,7 +177,10 @@ mergeInto(LibraryManager.library, {
     stream_ops: {
       read: function(stream, buffer, offset, length, position) {
         var contents = stream.node.contents;
+        if (position >= contents.length)
+          return 0;
         var size = Math.min(contents.length - position, length);
+        assert(size >= 0);
 #if USE_TYPED_ARRAYS == 2
         if (size > 8 && contents.subarray) { // non-trivial, and typed array
           buffer.set(contents.subarray(position, position + size), offset);
diff --git a/tests/unistd/io.c b/tests/unistd/io.c
index 0ff5f4fb..6bf22593 100644
--- a/tests/unistd/io.c
+++ b/tests/unistd/io.c
@@ -104,6 +104,12 @@ int main() {
   printf("errno: %d\n\n", errno);
   errno = 0;
 
+  printf("pread past end of file: %d\n", pread(f, readBuffer, sizeof readBuffer, 99999999999));
+  printf("data: %s\n", readBuffer);
+  memset(readBuffer, 0, sizeof readBuffer);
+  printf("errno: %d\n\n", errno);
+  errno = 0;
+
   printf("seek: %d\n", lseek(f, 3, SEEK_SET));
   printf("errno: %d\n\n", errno);
   printf("partial read from file: %d\n", read(f, readBuffer, 3));
diff --git a/tests/unistd/io.out b/tests/unistd/io.out
index 037d0c34..c979557e 100644
--- a/tests/unistd/io.out
+++ b/tests/unistd/io.out
@@ -31,6 +31,10 @@ read from file: 10
 data: 1234567890
 errno: 0
 
+pread past end of file: 0
+data: 
+errno: 0
+
 seek: 3
 errno: 0